Method for treating condensed vapor streams containing odorous compounds

ABSTRACT

The invention relates to methods and apparatuses for treating a condensate stream from a condenser that contains odorous compounds, such as various condensate streams produced in a rendering process. In one embodiment, the condensate stream is treated by adding an oxidizer to the liquid condensate stream to oxidize odor-causing compounds in the stream prior to being treated in a waste water pre-treatment system. In this manner, the odor resulting from these compounds can be reduced or eliminated.

This application is a continuation of U.S. application Ser. No.12/684,870 filed Jan. 8, 2010, which claims the benefit of U.S.Provisional Application No. 61/143,724, filed Jan. 9, 2009, theentireties of which are each hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to methods for treating condensed vapor streamscontaining odorous vapors. In particular, the invention relates tomethods for oxidizing condensate streams in, for example, rendering orpet food manufacturing facilities.

Description of Related Art

Control of odors is one of the most challenging problems faced by theanimal byproduct processing industry, referred to as rendering. In mostfacilities animal byproduct is brought into the processing facility andprocessed to, in some cases, manufacture animal feed. The processconverts the byproduct, which consists of waste animal tissue, intostable value-added material like purified animal fats (lard, tallow, andgrease) and protein meals (meat, bone meal, and blood meal). Generally,the process is performed by simultaneously drying the animal byproductand separating the fat from the bone and protein. In some cases, theanimal tissue may be blended with other organic material to form feeds.In some cases the animal byproduct includes feathers and hair, and theprocessing of these materials includes hydrolyzing and drying thematerial to form feather meal and a hair meal.

In the process of drying the animal byproduct, heat is added to thematerial resulting in the generation of vapors. These vapors carryodorous compounds such as hydrogen sulfide, ammonia, and volatileorganic compounds (VOCs). In most facilities an air scrubbing process isused to reduce or remove some of these odorous vapors prior to theirrelease into the atmosphere. In addition, various vapor streamscontaining these odorous compounds are condensed to separate as many ofthe condensable vapors from the non-condensable vapors prior to airscrubbing or release to the atmosphere. This greatly reduces the load tothe air scrubbing equipment and the environment. It should beappreciated that a rendering facility may generate multiple condensatestreams from various process steps. For example, condensate streams maybe produced from condensers used in conjunction with a cooker, anevaporator, a disk dryer, a spray dryer, drum dryer, or any otherprocess step in which a vapor stream is produced and can be condensed.

In the process of condensing a vaporous stream, a large portion of theodorous or odor causing compounds are separated prior to air scrubbingthereby forming one or more liquid condensate streams containing thesesoluble, odor causing compounds. The condensed vapor streams typicallyare mixed with other waste streams and processed using a waste waterpretreatment system, introduced into a biological system for processing,or discharged to a sewer system. In none of these cases, however, arethe condensed vapor or condensate streams treated for odor prior tobeing fed to the waste water pre-treatment system. Therefore, even aftermixing with other streams and being further processed prior todischarge, the soluble odor-causing compounds in these condensatestreams can be the cause of odor problems in the surrounding atmosphere.In many cases where the condensed vapors from the processing of theanimal byproduct material are mixed with other fluid systems andprocessed in a waste water pretreatment or in a biological treatmentsystem, the odor-causing compounds are liberated through reducedsolubility driven by changes in pH, temperature, mechanical aeration, orother means. Accordingly, once liberated, these compounds become anevident source of odor nuisance.

Therefore, there is a need for a method of treating the odor-causingcompounds in condensate streams, as such need exists in rendering andpet food processing facilities, as well as other industries that producevapor streams containing odor compounds that can be condensed, such asoil recovery processes.

BRIEF SUMMARY OF THE INVENTION

Generally, the invention and its various embodiments relate to methodsand apparatuses for treating vapor streams comprising odorous compounds.More specifically, these vapor streams are condensed along with at leastsome of the odorous compounds to generate a liquid stream that issubsequently oxidized to reduce its odor.

In some embodiments, the invention relates to methods and apparatusesfor treating a condensate stream from a condenser in a renderingprocess. Because the condensate streams generated in a rendering processcontain a significant amount of odor-causing compounds, these condensatestreams can be the cause of odor problems in the surrounding atmosphere,even after mixing with other liquid streams from the rendering processand after treatment of all of these combined streams prior to discharge.Accordingly, in one embodiment, a method for reducing odor-causingcompounds in a condensate stream from a rendering process comprisescondensing a vapor stream containing odorous compounds in a renderingprocess to produce a liquid condensate stream comprising solubleodor-causing compounds condensed from said vapor stream and adding anoxidizer to the condensate stream. As a result of adding an oxidizer,the odor-causing compounds are oxidized, thereby reducing the odor ofthe condensate stream. The oxidized condensate stream may then be fed toa waste water pre-treatment system or similar system or, in some cases,simply discharged.

In another embodiment, the oxidized condensate stream may optionally bemixed with other liquid streams from the rendering process and then fedto a waste water pre-treatment system or similar system, or in somecases, simply discharged. These other liquid streams may include anyliquid stream from the rendering process, including streams that areintended to be discharged as well as other condensate streams from therendering process that may also have been separately oxidized to removeodor-causing compounds. In other embodiments, these other condensatestreams may be added to the oxidized condensate stream without havingbeen oxidized or treated. In other embodiments, the oxidized condensatestream or streams can be added to the liquid effluent stream from awaste water pre-treatment system or similar system. It should beappreciated, again, that these various methods and apparatuses can beapplied to any condensate stream in the rendering process and that suchstreams can be combined and treated collectively or treated separatelyand combined before feeding to a waste water pre-treatment system or itsliquid effluent or before being discharged.

In other embodiments, a chelating agent may be added to the condensatestream to enhance the effectiveness of the oxidizer. For example, achelating agent may be added to the condensate stream to increase thesolubility of the oxidizer. Further, a chelating agent may be added tothe condensate stream to enhance the solubility of a catalyst that isadded to catalyze the oxidation of the condensate stream. Further still,a chelating agent may be added to prevent or reduce the formation ofundesirable complexes that may interfere with the oxidation. Forexample, in connection with the use of hydrogen peroxide as an oxidizerand the use of a metal-based catalyst to catalyses the decomposition ofthe hydrogen peroxide to form hydroxyl radicals, a semi-colloidal metalcomplex may form during the oxidation process that, in some instances,may be undesirable. A chelating agent may be added to prevent theformation of such metal hydroxides or other insoluble metal complexes.

By oxidizing a condensate stream containing odorous components, odortreatment costs can be reduced and odor-causing compounds can beoxidized to reduce or eliminate odor problems caused by these compounds.In addition, particular odor-causing compounds can be targeted fortreatment. Accordingly, any odor problems resulting from these compoundscan be reduced or eliminated.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a flow diagram for a typical rendering process;

FIG. 2 is a flow diagram of one embodiment of the present invention; and

FIG. 3 is a flow diagram of another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Some of the various embodiments of the invention are described below inconjunction with the Figures; however, this description should not beviewed as limiting the scope of the present invention. Rather, it shouldbe considered exemplary of various embodiments that fall within thescope of the present invention as defined by the claims. Further, itshould be appreciated that references to “the invention” or “the presentinvention” should not be construed as meaning that the descriptionherein is directed to only one embodiment or that every embodiment mustcontain a given feature described in connection with the use of suchphrases. In fact, various embodiments with common and differing featuresmay be described herein.

Generally, the invention and its various embodiments relate to methodsand apparatuses for treating vapor streams comprising odorous compounds.More specifically, these vapor streams are condensed along with at leastsome of the odorous compounds to generate a liquid stream that issubsequently oxidized to reduce its odor.

In some embodiments, the invention relates to methods and apparatusesfor treating a condensate stream from a condenser in a renderingprocess. Because the condensate stream generated in a rendering processcontains a significant amount of odor-causing compounds, this condensatestream can be the cause of odor problems in the surrounding atmosphere,even after mixing with other liquid streams from the rendering processand after treatment of all of these combined streams prior to discharge.Accordingly, in one embodiment, the condensate stream is treated toreduce odor and then optionally mixed with other liquid streams from therendering process, which may be sent to a waste water pre-treatmentsystem or, in some cases, discharged. Generally, the treatment of thecondensate stream to reduce its odor comprises oxidizing the condensatestream by adding an oxidizer, with the optional addition of a catalystto catalyze the oxidation and the optional addition of a chelating agentfor various purposes as described further below. As a result of addingan oxidizer, the odor-causing compounds are oxidized, thereby reducingthe odor of the condensate stream. The oxidized condensate stream maythen be fed to a waste water pre-treatment system or similar system or,in some cases, simply discharged.

In other embodiments, the oxidized condensate stream may optionally bemixed with other liquid streams from the rendering process and then fedto a waste water pre-treatment system or similar system, or in somecases, simply discharged. These other liquid streams may include anyliquid stream from the rendering process that is intended to bedischarged, as well as other condensate streams from the renderingprocess that may also have been separately oxidized to removeodor-causing compounds. In other embodiments, these other condensatestreams may be added to the oxidized condensate stream without havingbeen oxidized or treated. In other embodiments, the oxidized condensatestream or streams can be added to the liquid effluent stream from awaste water pre-treatment system or similar system. It should beappreciated, again, that these various methods and apparatuses can beapplied to any condensate stream in the rendering process and that suchstreams can be combined and treated collectively or treated separatelyand combined before feeding to a waste water pre-treatment system or itsliquid effluent or before being discharged. Each of these embodiments isdescribed in additional detail below in connection with the Figures.

FIG. 1 is a flow diagram for a typical rendering process. In thisprocess 100, a truck 102 will typically dump various animal byproductmaterial into a storage tank 104. This byproduct material is feed to acooker 106, or a rotary or disk dryer or hydrolizer, where heat is addedto dry the material or to drive off the water content and to separatethe fat from the bone and protein. As a result, the cooker 106 producesa vapor stream 108, an oils stream, and a solids stream 110 that isfurther processed into various products, such as animal feed. It shouldbe appreciated that if a rotary or disk dryer or hydrolizer is used thentypically only two streams are produced, a vapor stream and a solidsstream that also comprises oils.

The vapor stream 108 is passed to a condenser 112 where the vapor stream108 is cooled to condense the vapor stream, thereby separating as manyof the condensable vapors from the non-condensable vapors. The condenser112 produces a vapor stream 113 that is passed to an air scrubber 116where certain vaporous components are removed from the vapor. The airscrubber 116 then discharges the remaining vapor 118 to the atmosphere.It should be appreciated that instead of a scrubber 116, or incombination with a scrubber, the vapor stream 113 may be treated bypartially burning the vapor stream 113 in either a boiler as part of theair fed to the boiler for combustion, a thermal oxidizer (TO), or aregenerative thermal oxidizer (RTO) and then emitted to the atmosphereas an incompletely combusted exhaust stream or further treated using ascrubber.

The condenser 112 also produces a condensate stream 114 that is passedto a mix box 120 into which other process streams 122, 124 from therendering process 100 are added. The combination of all of these streamsin the mix box 120 is then passed to a waste water pre-treatment system126 that separates sludge 128, liquid 130, and solids 132 from eachother for discharge. It should be appreciated that the waste waterpre-treatment system 126 may be a diffused or induced air flotationsystem because the solids and oil are more likely to separate and floatthan separate and sink. In some cases pre-treatment may includebiological digestion of the soluble fraction that is measured asbiological oxygen demand, as well as the use of nitrifying bacteria toremove the nitrogen loading prior to surface discharge of discharge to amunicipality.

It should be appreciated that the use of a mix box 120, shown in FIG. 1with a dashed line, is optional since the condensate stream 114 may bepassed directly to the waste water pre-treatment system 126. Further anyadditional process streams 122, 124 may also be passed directly to thewaste water pre-treatment system 126. Alternatively, any of thecondensate stream 114 or other process streams 122, 124 may simply beadded to each other and passed to the waste water pre-treatment system126 without the use of a mix box 120.

It should be appreciated that the additional process streams 122, 124may be any process stream produced in the rendering process, including,for example, any liquid stream generated in the rendering process thatis intended to be discharged such as wash water as well as othercondensate streams from the rendering process that may also have beenseparately oxidized to remove odor-causing compounds. For example, anyvaporous stream produced through the processing of any animal parts towhich heat is added resulting in the generation of a vaporous streamthat would contain odorous components, at least a portion of which couldbe subsequently condensed.

FIG. 2 is a flow diagram of one embodiment of the present invention. Inthis rendering process 200 basically all of the same steps as describedabove in connection with FIG. 1 are used. However, the condensate stream114 is oxidized prior to being added to the mix box 120. By oxidizingthis condensate stream 114 odor-causing compounds can be oxidized toreduce or eliminate odor problems caused by these compounds therebyreducing odor treatment costs. Additional information regarding odorsand volatile organic compounds from a rendering plant are described in“Effect of a Packed-Bed Scrubber Using Radox Catalyst on the Emission ofOdors and Volatile Organic Compounds from a Commercial Poultry RenderingPlant,” by James A. Zahn and Jennifer Anhalt, April 2002, National SwineResearch and Information Center, USDA-ARS, 2150 Pammel Drive, Ames, Iowa50011, United States Department of Agriculture, the entirety of which ishereby incorporated by reference. It should be appreciated that theodorous compounds discussed in this paper are some of the compounds thatcan be oxidized according to the various embodiments of the presentinvention.

The oxidation of the condensate stream 114 can be accomplished by addingan oxidizer 202 directly to the condensate stream 114 upstream of themix box 120 thereby oxidizing the condensate stream 114 before it isadded to the mix box 120. Many oxidizers are available for thisoxidation step. For example, oxidizers that may be used include, but arenot limited to, bromine, chlorine, hypochlorous acid, chlorine dioxide,permanganate, ozone, perhydroxial radical, and hydrogen peroxide aloneor hydrogen peroxide and hydroxyl radicals generated by the addition ofhydrogen peroxide and a catalyst that catalyzes the decomposition ofhydrogen peroxide. Information regarding the addition of oxidizers andcatalysts to oxidize odorous and noxious components absorbed from a gasstream is described in U.S. patent application Ser. No. 11/442,554,entitled Method and Apparatus for Use of Reacted Hydrogen PeroxideCompounds in Industrial Process Waters (U.S. Publication No.2007/0059229), the entirely of which is hereby incorporated by referenceherein. It should be appreciated that multiple oxidizers may be used,including any combination of the foregoing named oxidizers.

The oxidizer 202 can be added directly to the condensate stream 114. Theaddition point in the condensate stream 114 where the oxidizer 202 isadded should be at a location upstream of the mix box 120 that providessufficient time for the oxidizer to contact and oxidize a desired amountof the odor-causing compounds prior to the condensate stream 114reaching the mix box 120. Accordingly, the addition point will bedetermined based upon the concentration of odor-causing compounds in thecondensate stream 114, the amount of oxidation desired, the amount ofoxidizer added, and the residence time available for oxidation to occur.One of skill in the art will appreciate how to optimize these parametersto achieve the optimal or desired reduction in odor.

It should also be appreciated that the oxidation of the condensatestream 114 may be performed in a separate tank by feeding the condensatestream 114 to an appropriately sized tank and adding the oxidizer to thetank. The oxidized condensate can then be fed from the tank to the mixbox 120. In this case, the tank may provide better control over themixing and contacting of the oxidizer with the odor-causing compounds.The tank should be appropriately sized to provide sufficient residencetime to accomplish the desired degree of oxidization based upon theconcentration of odor-causing compounds in the condensate stream 114,the amount of oxidation desired, and the amount of oxidizer added. Itshould be appreciated, however, that a portion of the oxidation may beperformed in a tank and additional oxidation may occur in the condensatestream 114 discharged from the tank. In other words, the tank does notnecessarily have to be sized to provide all of the desired oxidation andinstead can be sized such that the oxidation occurring in the tank aswell as in the condensate stream leaving the tank prior to its additionto the mix box provides the overall desired degree of oxidation.

In addition, a chelating agent may optionally be added to the condensatestream 114 for a variety of purposes. For example, in connection withthe use of hydrogen peroxide as an oxidizer and the use of a metal-basedcatalyst to catalyze the decomposition of the hydrogen peroxide to formhydroxyl radicals, a semi-colloidal metal complex may form during theoxidation process, and in some instances, the development of thiscolloidal metal complex is undesirable. A chelating agent may be addedto prevent the formation of metal hydroxides or other insoluble metalcomplexes. In one embodiment, the chelating agent may be organic acidssuch as gluconic acids, glycolic acids, lactic acids, and combinationsthereof. It will be appreciated that the chelating agent may be selectedfrom a large number of available chelating agents; however, thechelating agent should not be of such potent chelating ability as toprevent the availability of the metal complex for decompositionpurposes.

Chelating agents can also be selected and used based upon the particularoxidizer being used. For example, a chelating agent may be added toenhance the solubility of the oxidizer or any catalyst that is used inconjunction with the oxidizer. For example, chelating agents known inthe art may be used to increase the solubility of metal-based catalysts,such as ferrous ion and other metal complexes, particularly useful inconjunction with the use of hydrogen peroxide as the oxidizer. Inaddition, ferric (Fe³⁺) ion may be used to decompose hydrogen peroxideto produce hydroxyl radicals, and chelating agents may be added toincrease the solubility of the ferric ion, thereby increasing theproduction of hydroxyl free radicals. Chemical Treatment of PesticideWastes—Evaluation of Fe(III) Chelates for Catalytic Hydrogen PeroxideOxidation of 2,4-D at Circumneutral pH, Sun et al., J. Agric. FoodChem., 1992, 40, 322-327, the entirety of which is hereby incorporatedby reference herein, describes several chelating agents that may be usedto solubilize ferric ion. Such chelating agents that showed “high”catalytic activity and that may be used include: aminopolycarboxylates,such as nitrilotriacetic acid and hydroxyethyliminodiacetic acid;N-heteroxcyclic carboxylates, such as picolinic acid; polyhydroxyaromatics, such as gallic acid; and other compounds, such as rhodizonicacid, tetrahydroxy-1,4-quinone, and hexaketocyclohexane. Anotherchelating agent that may be used is ferric methylglycinediacetate(Fe-MGDA), which is further described in U.S. Pat. No. 6,960,330, theentirety of which is hereby incorporated by reference herein. Thesechelating agents may be used separately; however, it may be possible touse mixtures of these chelating agents as well. The use of chelatingagents in connection with the scrubbing of oxidize odorous and noxiouscomponents from gas streams is described in U.S. patent application Ser.No. 11/442,554, entitled Method and Apparatus for Use of ReactedHydrogen Peroxide Compounds in Industrial Process Waters (U.S.Publication No. 2007/0059229), the entirety of which is herebyincorporated by reference herein.

There are several methods by which a chelating agent may be added. FIG.2 illustrates the optional addition of a chelating agent 204 directly tothe condensate stream 114. FIG. 2 also illustrates the optional additionof a catalyst 206 either directly to the condensate stream 114 or byadding it to the chelating agent 204. In either case, the chelatingagent 204 and the catalyst 206 are added to the condensate stream 114separately from the oxidizer 202. In the embodiment in which thechelating agent 204 and the catalyst 206 are added together prior tobeing added to the condensate stream 114, the combined chelating agent204 and catalyst 206 should be added near the addition point of theoxidizer 202 and may be added immediately adjacent to the addition pointof the oxidizer 202, either upstream or downstream of the addition pointof the oxidizer 202. It should be appreciated that the mixing of thechelating agent and catalyst should be done in a manner to providesufficient time for chelation to occur prior to adding this mixture tothe condensate stream 114. Also, as shown in FIG. 2, each of thechelating agent 204, the catalyst 206, and the oxidizer 202 may be addedseparately to the condensate stream 114, noting that their relativeaddition points should be such that sufficient time is provided forchelation to occur to optimize catalyst activity. One of skill in theart will appreciate that the concentration and feed rates of thechelating agent and any catalyst can be optimized in conjunction withthe concentration and feed rate of the oxidizer to provide the desireddegree of oxidation, depending upon the addition point of the chelatingagent and any catalyst and the oxidizer into the condensate stream 114.

If the condensate stream 114 is oxidized in a tank, the chelating agent204 may be added to any catalyst 206, and the resulting mixture added tothe tank separately from the addition of the oxidizer 202 to the tank.In this case, again, mixing of the chelating agent 204 and catalyst 206should be done to provide sufficient time for chelation to occur priorto adding this mixture to the condensate stream 114 in the oxidationtank. In yet another embodiment, each of these components may be addedseparately to the tank. One of skill in the art will appreciate that theconcentration and feed rates of the chelating agent and any catalystinto the tank can be optimized in conjunction with the concentration andfeed rate of the oxidizer into the tank and the size and residence timeof the tank to provide the desired degree of oxidation.

As described above, when using a catalyst with the oxidizer, thechelating agent and the catalyst, such as ferrous ion or ferric ion(which may be added, for example, as ferric sulfate) may be mixed beforeuse to allow for chelation. In this case, the selection of the catalysisand the chelating agent can be based upon the specific application orparticular components to be oxidized. By mixing the catalyst and thechelating agent prior to use, this mixture is essentially “tailor-made”and is ready for immediate use in the particular application at issue.In fact, this mixture can be prepared remote from the facility where itwill be used and shipped to that facility for immediate use.

In some embodiments, control over the desired degree of oxidation can beaccomplished using colorimetric measurement of one or more odor causingcompounds. In this case, oxidation of a given odor causing compound toan end point could be used to adjust the concentration and feed rate ofthe oxidizer, the chelating agent, or both for a given addition point ortank size.

In some embodiments, an electrode could be used to monitor theconcentration of a given odor causing compound, or its absorbed form, tosimilarly adjust the feed rate of the oxidizer, the chelating agent, orboth for a given addition point or tank size. For example, a THERMOORION silver/sulfide ion selective electrode could be used to monitorsulfide (i.e., a measure of solubilized hydrogen sulfide), and the feedrate of the oxidizer could be adjusted based on the presence of sulfideas measured by the probe.

In some embodiments, hydrogen peroxide can be used as the oxidizer. Inthis case, a hydrogen peroxide sensing system could be used to monitorthe hydrogen peroxide addition rate. For example, a PROMINENT DULCOTROLPEROX 20 hydrogen peroxide sensing and control system or the like couldbe used to control the addition of hydrogen peroxide, particularly inthose cases where conventional use of ORP (oxidation reductionpotential) is ineffective at monitoring either hydrogen peroxideaddition or the decomposition of the hydrogen peroxide with a catalyst.In one embodiment, hydrogen peroxide could be added at a rate to simplymaintain a detectable amount of hydrogen peroxide using this controlsystem. It should be appreciated, however, that ORP may be used tocontrol the addition rate of the oxidizer. In this case, the ORPmeasurement can be used to determine whether additional oxidizer isrequired to provide the requisite oxidation residual potential.

Similar to the process shown in FIG. 1, the condensate stream 114, afterhaving been oxidized, is passed to a mix box 120 into which otherprocess streams 122, 124 from the rendering process 100 are added. Asdescribed above, these additional process streams 122, 124 may includeany stream produced in the rendering process, including streams that areintended to be discharged, as well as other condensate streams from therendering process that may also have been separately oxidized to removeodor-causing compounds. For example, such condensate streams may includeany condensate stream produced from a vaporous stream generated in therendering process, such as any vaporous stream generated by the heatingof animal parts, other than the cooker 106, that may also containodorous components. These other condensate streams may be added to theoxidized condensate stream 114 without having been oxidized or treated.Alternatively, one or more of these other condensate streams may betreated, separately or in combination, through oxidation in the samemanner as the condensate stream 114 from the cooker 106. In fact, itshould be appreciated that although this description is focusedprimarily on the condensate stream 114 from the cooker 106, the variousembodiments described herein apply equally to any other condensatestream containing odorous compounds that is generated, or that could begenerated, in the rendering process.

As described above in connection with FIG. 1, the use of the mix box 120in the process shown in FIG. 2 is also optional. Accordingly, thecondensate stream 114 may be passed directly to the waste waterpre-treatment system 126. Further any additional process streams 122,124 may also be passed directly to the waste water pre-treatment system126. Alternatively, any of the condensate stream 114 or other processstreams 122, 124 may simply be added to each other and passed to thewaste water treatment system 126 without the use of a mix box 120.

FIG. 3 is a flow diagram of another embodiment of the present invention.The process 300 shown in FIG. 3 is similar to that shown in FIG. 2, withthe exception that the oxidized condensate stream 114 is added directlyto the effluent liquid stream 130 produced by the waste waterpre-treatment system 126. This embodiment provides the ability topotentially lower the biological oxygen demand of the effluent liquidstream 130 due to the addition of the oxidized condensate stream 114.Further, since the effluent liquid stream 130 from the waste waterpre-treatment system 126 typically requires the addition of acid toreduce its pH prior to discharge, the addition of the oxidizedcondensate stream 114 may reduce the amount of acid required to reducethe pH. This occurs because the condensate stream 114 typically has arelatively high concentration of ammonia and, therefore, a relativelyhigh pH. Further still, by adding the oxidized condensate stream 114downstream of the waste water pre-treatment system 126, the load on thewaste water pre-treatment system 126 is reduced, thereby reducing thewear on the waste water pre-treatment system 126 and potentiallyreducing operating and maintenance costs.

In this embodiment, other streams 122, 124, as described above, but, inparticular, other condensate streams from the rendering process thatalso have been separately oxidized to remove odor-causing compounds, canoptionally be added to the liquid effluent stream 130 from the wastewater pre-treatment system 126 or similar system. It should beappreciated, that these other streams 122, 124 can be added directly tothe condensate stream 114 or separately to the liquid effluent stream130. Further, as described above, one or more of these condensatestreams can be combined and treated collectively by oxidation asdescribed in connection with FIG. 2 and then added to the liquideffluent stream 130.

While the foregoing description has generally been in the context of acondensate stream in a rendering facility, it should be appreciated thatthe process and methods described herein may have application intreating other liquid streams containing dissolved odorous compounds.For example, such streams exist in the pet food manufacturing industryand animal kill plants, and these streams can be similarly treated usingthe various embodiments of the invention described herein. Therefore,the foregoing description should not be viewed as limited to therendering industry or any particular liquid stream and may haveapplication for any vapor stream generated by a process that has an odorload that is condensable and that can be oxidized, such as oil recoveryprocesses.

What is claimed is:
 1. A method for reducing odor causing compounds in acondensate stream from a rendering process, comprising: generating avapor stream from a cooker in a rendering process; condensing said vaporstream to produce a liquid condensate stream comprising at least onesoluble odor-causing compound condensed from said vapor stream; addingan oxidizer to said condensate stream to oxidize the at least onesoluble odor-causing compound; and mixing said condensate stream with atleast one other liquid stream from the rendering process.
 2. The methodof claim 1, further comprising adding a chelating agent to saidcondensate stream.
 3. The method of claim 1, further comprising adding acatalyst to said condensate stream.
 4. The method of claim 1, furthercomprising: mixing a chelating agent and a catalyst together to producea mixture of said chelating agent and said catalyst; and adding saidmixture of said chelating agent and said catalyst to said condensatestream.
 5. The method of claim 4, wherein said oxidizer compriseshydrogen peroxide and said catalyst comprises ferrous or ferric ion. 6.The method of claim 1, wherein said mixing produces a combined liquidstream and further comprising passing said combined liquid stream to awaste-water pre-treatment system.
 7. The method of claim 1, wherein saidmixing produces a combined liquid stream and further comprising passingsaid combined liquid stream to a discharge stream from a waste-waterpre-treatment system.
 8. The method of claim 7, wherein said passingproduces a combined discharge stream having a lower biological oxygendemand than said discharge stream.
 9. The method of claim 1, whereinsaid mixing is performed in a mix box and said adding comprises addingsaid oxidizer directly to said condensate stream at a point upstream ofthe mix box to provide sufficient time to oxidize at least a portion ofthe soluble odor-causing compounds in said condensate stream prior tosaid mixing.
 10. The method of claim 1, wherein said adding is performedin a tank.
 11. A method for reducing odor causing compounds generated ina rendering process, comprising: condensing a vapor stream comprising aplurality of odor-causing compounds, thereby producing a liquidcondensate stream comprising a plurality of odor-causing compounds,wherein said vapor stream comprises a vapor stream from any equipmentused in a rendering process that produces vapor prior to the addition ofan oxidizer to said condensate stream; adding an oxidizer to saidcondensate stream in a location separate from said equipment; mixingsaid condensate stream with at least one other liquid stream from therendering process.
 12. The method of claim 11, further comprising addinga chelating agent to said condensate stream.
 13. The method of claim 11,further comprising adding a catalyst to said condensate stream.
 14. Themethod of claim 11, further comprising: mixing a chelating agent and acatalyst together to produce a mixture of said chelating agent and saidcatalyst; and adding said mixture of said chelating agent and saidcatalyst to said condensate stream.
 15. The method of claim 14, whereinsaid oxidizer comprises hydrogen peroxide and said catalyst comprisesferrous or ferric ion.
 16. The method of claim 11, wherein said mixingproduces a combined liquid stream and further comprising passing saidcombined liquid stream to a waste-water pre-treatment system.
 17. Themethod of claim 11, wherein said mixing produces a combined liquidstream and further comprising passing said combined liquid stream to adischarge stream from a waste-water pre-treatment system.
 18. The methodof claim 17, wherein said passing produces a combined discharge streamhaving a lower biological oxygen demand than said discharge stream. 19.The method of claim 11, wherein said mixing is performed in a mix boxand said adding comprises adding said oxidizer directly to saidcondensate stream at a point upstream of the mix box to providesufficient time to oxidize at least a portion of the solubleodor-causing compounds in said condensate stream prior to said mixing.20. The method of claim 11, wherein said equipment comprises one or moreof a cooker, a dryer, and a hydrolizer and wherein said adding isperformed in a tank.